以植物为分析对象,来了解城市中空气受污染的状况和程度、污染物质的成分及其分布,这是近几年西方国家十分推崇的一种环境监测方法。多年以前,人们便发现,有些植物对于污染物极为敏感,对空气污染能起到“预警”作用,这类植物便被称为“指示植物”。譬如,牵牛花中含有花青素,该色素在碱性溶液中为蓝色,在酸性溶液中为红色。从早晨到晚上,随着二氧化碳含量的增加,牵牛花对二氧化碳的吸收量也随之加大,花中的酸性不断提高,从而造成花色由蓝变红,牵牛花也就成了能对空气中二氧化碳浓度监测的指示性植 Taking plants as the object of analysis to understand the status and degree of air pollution in cities, the composition and distribution of pollutants, which is an environmental monitoring method highly praised by western countries in recent years. Years ago, people found that some plants are extremely sensitive to pollutants and play an “early warning” role in air pollution. Such plants are called “plant-pointing plants.” For example, morning glory contains anthocyanins that are blue in alkaline solution and red in acidic solution. Morning to night, with the increase of carbon dioxide content, morning glory also increased the absorption of carbon dioxide, the flowers continue to increase the acidity, resulting in the color from blue to red, morning glory has become able to Indication of carbon dioxide concentration monitoring in air